[owltown]

Does the GLC300 require a battery tender for a car not driven all the time?
If true, what type and size its needed?

 

[CRNCYX]

All vehicles require it any time you have it sitting for a long time.

While you can do the math and figure out what sort of amps it needs on a consistent basis most of the popular trickle chargers charge at a rate which is safe for all batteries. So you can either go that "universal" route or check with MB to see what they recommend and can supply you with.

 

[Klass]

When you say not driven all the time, how long is it left sitting, and when you drive it, how long is it operating for?